1. Field
Embodiments disclosed herein generally relate to a magnetic write head for use in a hard disk drive.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic media, such as a disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent a media facing surface (MFS), such as an air bearing surface (ABS) of the slider, causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
In a perpendicular magnetic recording system, the magnetic media has a magnetically soft underlayer covered by a thin magnetically hard top layer. The perpendicular write head has a write pole with a very small cross section and a return pole having a much larger cross section. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where the magnetic flux is sufficiently spread out and weak that the signal recorded by the write pole is not erased.
During the writing operations, which is a dynamic process, the write field generated not only records on the track of interest but also on the adjacent tracks leading to data erasure. This erasure is often due to inadequate shielding or improper magnetization direction of the shields during the writing process. In a controlled experiment, a very high percentage of the hard disk drives that failed for far track interference (FTI) were found to have the magnetization direction in the trailing shield reversed of what is normally expected. Slider level initiation may help, but it is very difficult to implement in production. In addition, even if sliders are initialized, domains in the shields can still change after building heads into hard disk drives.
Therefore, an improved magnetic write head is needed.